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Journal of Biomechanics

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https://www.readbyqxmd.com/read/29050823/nonlinear-vibrations-of-pre-and-post-buckled-lipid-supramolecular-micro-nano-tubules-via-nonlocal-strain-gradient-elasticity-theory
#1
S Sahmani, M M Aghdam
The unique geometry with high surface ratio makes lipid micro/nano-tubules as an excellent self-assembled supramolecular structure in various biological applications such as controllable release systems and drug delivery. In the present study, the size-dependent nonlinear vibrations of axially loaded lipid micro/nano tubules associated with the both prebuckling and postbuckling domains are explored comprehensively. To accomplish this purpose, the nonlocal strain gradient theory of elasticity including simultaneously two entirely different features of size dependency is utilized within the framework of the third-order shear deformable beam model...
October 9, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29050821/chiral-behavior-in-rat-tail-tendon-fascicles
#2
Kimberly A Buchanan, Roderic S Lakes, Ray Vanderby
Ex vivo tendon mechanical behavior has been well described under rotationally constrained uniaxial tensile testing. During standard loading of rat tail tendon (RTT) fascicles, apparent axial twist has been observed. To quantify this behavior, we designed a custom testing setup, utilizing magnetic suspension, to allow unconstrained axial rotation during tensile loading. We characterized the rotational behavior of single and paired RTT fascicles under cyclic loading. We also measured stress relaxation across loading cycles as well as "rotational relaxation"...
October 7, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29050822/a-comparison-and-update-of-direct-kinematic-kinetic-models-of-leg-stiffness-in-human-running
#3
Bernard X W Liew, Susan Morris, Ashleigh Masters, Kevin Netto
Direct kinematic-kinetic modelling currently represents the "Gold-standard" in leg stiffness quantification during three-dimensional (3D) motion capture experiments. However, the medial-lateral components of ground reaction force and leg length have been neglected in current leg stiffness formulations. It is unknown if accounting for all 3D would alter healthy biologic estimates of leg stiffness, compared to present direct modelling methods. This study compared running leg stiffness derived from a new method (multiplanar method) which includes all three Cartesian axes, against current methods which either only include the vertical axis (line method) or only the plane of progression (uniplanar method)...
October 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29042057/urethral-lumen-occlusion-by-artificial-sphincteric-device-evaluation-of-degraded-tissues-effects
#4
Arturo Nicola Natali, Chiara Giulia Fontanella, Silvia Todros, Emanuele Luigi Carniel
Urinary incontinence can be surgically treated by means of artificial sphincters, based on a cuff that provides a pressure around the urethra to occlude the lumen. Considering the frequent access of elderly patients to this surgical practice, tissue degradation phenomena must be investigated, since they could affect treatment reliability and durability. The potential degradation can be interpreted considering a variation within soft tissue constitutive formulation, by means of a correlation between mechanical properties and tissues ageing...
October 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29042056/a-computational-model-of-the-hepatic-circulation-applied-to-analyze-the-sensitivity-of-hepatic-venous-pressure-gradient-hvpg-in-liver-cirrhosis
#5
Tianqi Wang, Fuyou Liang, Zunqiang Zhou, Lu Shi
Measurement of hepatic venous pressure gradient (HVPG) is currently widely adopted to provide an estimate of portal pressure gradient (PPG) in the diagnosis and treatment of portal hypertension associated with liver cirrhosis. Despite the well-documented clinical utility of HVPG, it remains poorly understood how the relationship between HVPG and PPG is affected by factors involved in the pathogenesis and progression of cirrhosis. In the study, a computational model of the hepatic circulation calibrated to in vivo data was developed to simulate the procedure of HVPG measurement and quantitatively investigate the error of HVPG relative to PPG under various pathophysiological conditions...
October 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29037443/a-comprehensive-assessment-of-the-musculoskeletal-system-the-cams-knee-data-set
#6
William R Taylor, Pascal Schütz, Georg Bergmann, Renate List, Barbara Postolka, Marco Hitz, Jörn Dymke, Philipp Damm, Georg Duda, Hans Gerber, Verena Schwachmeyer, Seyyed Hamed Hosseini Nasab, Adam Trepczynski, Ines Kutzner
Combined knowledge of the functional kinematics and kinetics of the human body is critical for understanding a wide range of biomechanical processes including musculoskeletal adaptation, injury mechanics, and orthopaedic treatment outcome, but also for validation of musculoskeletal models. Until now, however, no datasets that include internal loading conditions (kinetics), synchronized with advanced kinematic analyses in multiple subjects have been available. Our goal was to provide such datasets and thereby foster a new understanding of how in vivo knee joint movement and contact forces are interlinked - and thereby impact biomechanical interpretation of any new knee replacement design...
October 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29037442/estimation-of-in-vivo-inter-vertebral-loading-during-motion-using-fluoroscopic-and-magnetic-resonance-image-informed-finite-element-models
#7
Sahand Zanjani-Pour, Judith R Meakin, Alex Breen, Alan Breen
Finite element (FE) models driven by medical image data can be used to estimate subject-specific spinal biomechanics. This study aimed to combine magnetic resonance (MR) imaging and quantitative fluoroscopy (QF) in subject-specific FE models of upright standing, flexion and extension. Supine MR images of the lumbar spine were acquired from healthy participants using a 0.5 T MR scanner. Nine 3D quasi-static linear FE models of L3 to L5 were created with an elastic nucleus and orthotropic annulus. QF data was acquired from the same participants who performed trunk flexion to 60° and trunk extension to 20°...
October 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29029957/a-model-based-approach-for-estimation-of-changes-in-lumbar-segmental-kinematics-associated-with-alterations-in-trunk-muscle-forces
#8
Iman Shojaei, Navid Arjmand, Judith R Meakin, Babak Bazrgari
The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs...
October 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29050824/in-vivo-repeatability-of-the-pulse-wave-inverse-problem-in-human-carotid-arteries
#9
Matthew McGarry, Pierre Nauleau, Iason Apostolakis, Elisa Konofagou
Accurate arterial stiffness measurement would improve diagnosis and monitoring for many diseases. Atherosclerotic plaques and aneurysms are expected to involve focal changes in vessel wall properties; therefore, a method to image the stiffness variation would be a valuable clinical tool. The pulse wave inverse problem (PWIP) fits unknown parameters from a computational model of arterial pulse wave propagation to ultrasound-based measurements of vessel wall displacements by minimizing the difference between the model and measured displacements...
September 27, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29033002/fiber-orientation-effects-in-simple-shearing-of-fibrous-soft-tissues
#10
Cornelius O Horgan, Jeremiah G Murphy
Fiber-reinforcement is a common feature of many soft biological tissues. Continuum mechanics modeling of the mechanical response of such tissues using transversely isotropic hyperelasticity is now well developed. The fundamental deformation of simple shear within this framework is examined here. It is well known that the normal stress effect characteristic of nonlinear elasticity plays a crucial role in maintaining a homogeneous deformation state in the bulk of the specimen. Here we consider the effect of anisotropy and fiber-orientation on the shear and normal stresses...
September 27, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28985894/in-vivo-fascicle-length-measurements-via-b-mode-ultrasound-imaging-with-single-vs-dual-transducer-arrangements
#11
Scott F Brennan, Andrew G Cresswell, Dominic J Farris, Glen A Lichtwark
Ultrasonography is a useful technique to study muscle contractions in vivo, however larger muscles like vastus lateralis may be difficult to visualise with smaller, commonly used transducers. Fascicle length is often estimated using linear trigonometry to extrapolate fascicle length to regions where the fascicle is not visible. However, this approach has not been compared to measurements made with a larger field of view for dynamic muscle contractions. Here we compared two different single-transducer extrapolation methods to measure VL muscle fascicle length to a direct measurement made using two synchronised, in-series transducers...
September 25, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29037441/impact-of-ankle-foot-orthosis-stiffness-on-achilles-tendon-and-gastrocnemius-function-during-unimpaired-gait
#12
Hwan Choi, Keshia M Peters, Michael B MacConnell, Katie K Ly, Eric S Eckert, Katherine M Steele
Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular conditions and have also been used to reduce energy costs of walking for unimpaired individuals. AFOs influence joint motion and metabolic cost, but how they impact muscle function remains unclear. This study investigated the impact of different stiffness AFOs on medial gastrocnemius muscle (MG) and Achilles tendon (AT) function during two walking speeds. We performed gait analyses for eight unimpaired individuals. Each individual walked at slow and very slow speeds with a 3D printed AFO with no resistance (free hinge condition) and four levels of ankle dorsiflexion stiffness: 0...
September 23, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28985893/metabolic-responses-induced-by-compression-of-chondrocytes-in-variable-stiffness-microenvironments
#13
Carley N McCutchen, Donald L Zignego, Ronald K June
Cells sense and respond to mechanical loads in a process called mechanotransduction. These processes are disrupted in the chondrocytes of cartilage during joint disease. A key driver of cellular mechanotransduction is the stiffness of the surrounding matrix. Many cells are surrounded by extracellular matrix that allows for tissue mechanical function. Although prior studies demonstrate that extracellular stiffness is important in cell differentiation, morphology and phenotype, it remains largely unknown how a cell's biological response to cyclical loading varies with changes in surrounding substrate stiffness...
September 21, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29031524/analysis-of-pelvic-strain-in-different-gait-configurations-in-a-validated-cohort-of-computed-tomography-based-finite-element-models
#14
Zoryana Salo, Maarten Beek, David Wright, Asmaa Maloul, Cari Marisa Whyne
The pelvis functions to transmit upper body loads to the lower limbs and is critical in human locomotion. Semi-automated, landmark-based finite element (FE) morphing and mapping techniques eliminate the need for segmentation and have shown to accelerate the generation of multiple specimen-specific pelvic FE models to enable the study of pelvic mechanical behaviour. The purpose of this research was to produce an experimentally validated cohort of specimen-specific FE models of the human pelvis and to use this cohort to analyze pelvic strain patterns during gait...
September 19, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28958634/effect-of-noise-and-filtering-on-largest-lyapunov-exponent-of-time-series-associated-with-human-walking
#15
Sina Mehdizadeh, Mohammad Ali Sanjari
This study aimed to determine the effect of added noise, filtering and time series length on the largest Lyapunov exponent (LyE) value calculated for time series obtained from a passive dynamic walker. The simplest passive dynamic walker model comprising of two massless legs connected by a frictionless hinge joint at the hip was adopted to generate walking time series. The generated time series was used to construct a state space with the embedding dimension of 3 and time delay of 100 samples. The LyE was calculated as the exponential rate of divergence of neighboring trajectories of the state space using Rosenstein's algorithm...
September 19, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28988680/macroscopic-anisotropic-bone-material-properties-in-children-with-severe-osteogenesis-imperfecta
#16
Carolyne Albert, John Jameson, Sergey Tarima, Peter Smith, Gerald Harris
Children with severe osteogenesis imperfecta (OI) typically experience numerous fractures and progressive skeletal deformities over their lifetime. Recent studies proposed finite element models to assess fracture risk and guide clinicians in determining appropriate intervention in children with OI, but lack of appropriate material property inputs remains a challenge. This study aimed to characterize macroscopic anisotropic cortical bone material properties and investigate relationships with bone density measures in children with severe OI...
September 14, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28964498/in-vitro-culture-increases-mechanical-stability-of-human-tissue-engineered-cartilage-constructs-by-prevention-of-microscale-scaffold-buckling
#17
Jill M Middendorf, Sonya Shortkroff, Caroline Dugopolski, Stephen Kennedy, Joseph Siemiatkoski, Lena R Bartell, Itai Cohen, Lawrence J Bonassar
Many studies have measured the global compressive properties of tissue engineered (TE) cartilage grown on porous scaffolds. Such scaffolds are known to exhibit strain softening due to local buckling under loading. As matrix is deposited onto these scaffolds, the global compressive properties increase. However the relationship between the amount and distribution of matrix in the scaffold and local buckling is unknown. To address this knowledge gap, we studied how local strain and construct buckling in human TE constructs changes over culture times and GAG content...
September 14, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28964497/are-there-characteristic-motion-patterns-in-the-lumbar-spine-during-flexion
#18
Thomas Zander, Maxim Bashkuev, Hendrik Schmidt
Flexion is the main motion of the lumbar spine. While in vitro tests with pure moments suggest larger intra-segmental rotations for the more caudal segments, in vivo results show diverging motion distributions. The present study analysed the motion distribution in vivo of 320 asymptomatic subjects. The change of the back curvature between standing and upper body flexion was determined using a non-invasive measurement device. Linear, bilinear, trilinear, quadratic, and cubic regression models were fitted to the segmental motion distribution over the lengths of the lordosis to categorise characteristic motion patterns...
September 14, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28951045/the-equivalence-of-multi-axis-spine-systems-recommended-stiffness-limits-using-a-standardized-testing-protocol
#19
Timothy P Holsgrove, Dhara B Amin, Sonia Ramos Pascual, Boyin Ding, William C Welch, Sabina Gheduzzi, Anthony W Miles, Beth A Winkelstein, John J Costi
The complexity of multi-axis spine testing often makes it challenging to compare results from different studies. The aim of this work was to develop and implement a standardized testing protocol across three six-axis spine systems, compare them, and provide stiffness and phase angle limits against which other test systems can be compared. Standardized synthetic lumbar specimens (n=5), comprising three springs embedded in polymer at each end, were tested on each system using pure moments in flexion-extension, lateral bending, and axial rotation...
September 14, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28947160/model-based-inverse-estimation-for-active-contraction-stresses-of-tongue-muscles-using-3d-surface-shape-in-speech-production
#20
Narihiko Koike, Satoshi Ii, Tsukasa Yoshinaga, Kazunori Nozaki, Shigeo Wada
This paper presents a novel inverse estimation approach for the active contraction stresses of tongue muscles during speech. The proposed method is based on variational data assimilation using a mechanical tongue model and 3D tongue surface shapes for speech production. The mechanical tongue model considers nonlinear hyperelasticity, finite deformation, actual geometry from computed tomography (CT) images, and anisotropic active contraction by muscle fibers, the orientations of which are ideally determined using anatomical drawings...
September 14, 2017: Journal of Biomechanics
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